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UserspaceEmulator: Recognize xor/sub zeroing idioms and don't taint
"xor reg,reg" or "sub reg,reg" both zero out the register, which means we know for sure the result is 0. So mark the value as initialized, and make sure we don't taint the CPU flags. This removes some false positives from the uninitialized memory use detection mechanism. Fixes #2850.
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3 changed files with 72 additions and 38 deletions
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@ -59,6 +59,16 @@ public:
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return (m_shadow & 0x01) != 0x01;
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}
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void set_initialized()
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{
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if constexpr (sizeof(T) == 4)
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m_shadow = 0x01010101;
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if constexpr (sizeof(T) == 2)
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m_shadow = 0x0101;
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if constexpr (sizeof(T) == 1)
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m_shadow = 0x01;
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}
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private:
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T m_value;
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T m_shadow;
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